This invention relates to a battery-powered device for testing the static conductivity or resistivity of elastomeric articles. U.S. Pat. No. 3,963,981 to Vis discloses a leakage and continuity tester for testing medical instruments for ground impedance and leakage current. U.S. Pat. No. 3,784,906 to Ironside, discloses a multiple null bridge that uses amplifiers to test a known resistance against an unknown resistance.
In certain applications the static conductivity of a hose or belt can be critical to the safety of the work environment. A build-up of static charge in a hose or belt that is in service within a hazardous atmosphere can result in an explosion. The Rubber Manufacturers Association (RMA) has promulgated standards for the maximum acceptable resistivity of elastomeric belts in a hazardous atmosphere. A device that can determine if an elastomeric article meets this standard is necessary to ensure safe operation in a hazardous atmosphere. For example, a hose with two wires running throughout its length is only conductive if the same wire is grounded to the couplings at each end. A testing device such as the one disclosed herein, can verify to the operator that the hose is connected properly, ensuring safe operation.
A testing device that provides a readout of the resistivity or conductivity of an elastomeric article is complex to interpret and calibrate. For example, the RMA test for belt conductivity requires that the belt have a resistivity of 6 megohms or less when 500 volts is applied a specified distance across the article. There are different predetermined industry standards for testing nonconductivity as well as for testing the resistivity and conductivity of hose articles. Since there are many tests, and each test has a different threshold value that determines whether an article passes or fails the test, a device which only provides the actual resistivity of the article being tested is somewhat difficult for the operator to interpret. Since the primary purpose of a testing device of this type is to determine if the article is suitable for a particular service, a read-out of pass/fail has more significance to the operator than the read-out of the actual resistivity of the article. A device that provides a pass/fail readout for various elastomeric articles being tested for resistivity or conductivity was deemed highly desireable. Such a device is the object of the invention.